Removable antihalation layers for photographic film



July 9, 1968 G. c. GANDY ETAL 3,392,022

REMOVABLE ANTIHALATION LAYERS FOR PHOTOGRAPHIC FILM Filed Sept. 16, 1966 A's/L VER HAL/DE EMULSION SUPPORT ANTI-HALATIOIV COAT/N6 COMPRISING C A HEXAHYDROPHTHALATE 0/? C A TETRAHYDROPHTHALATE WITH ANTI-HALATION MATERIAL United States Patent "ice 3,392,022 REMOVABLE ANTIHALATION LAYERS FOR PHOTOGRAPHIC FILM Gerald C. Gandy and George W. Pierce, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Continuation-impart of application Ser. No. 400,028, Sept. 29, 1964. This application Sept. 16, 1966, Ser. No. 580,084

20 Claims. (Cl. 96-84) ABSTRACT OF THE DISCLOSURE Cellulose esters which contain hydrogenated phthalyl moieties as components for antihalation compositions.

This application is a continuation-in-part of our copending application Ser. No. 400,028, filed Sept. 29, 1964, now abandoned.

This invention relates to photographic film supplied with a removable antihalation layer comprising cellulose mixed esters containing radicals such as hexahydrophthalyl or tetrahydrophthalyl. More particularly, the invention relates to such film having an antihalation backing layer especially adapted for easy removability comprising cellulose acetate hexahydrophthalate or cellulose acetate tetrahydrophthalate in admixture with an alkylmethac-rylate-methacrylic acid copolymer and an antihalation material such as a dye.

The need for antihalation layers on photographic films is Well recognized. Many proposals have been made for overcoming halation. Usually the adverse effects from halation are minimized with a light absorbing layer on one of the surfaces of the photographic support, such as a backing layer, whereby the rays which would otherwise be reflected into the photosensitive layer are absorbed. One type of backing layer contains carbon or graphite dispersed in the backing material. Colloidal carbon dispersions useful in antihalation backings have been described in Staud et al. US. Patent No. 2,271,234, issued Jan. 27, 1942. Another type of antihalation layer is one which contains a colored material such as a dye which absorbs much of the visible spectrum.

Various alkali soluble materials have been referred to as useful carriers for antihalation materials such as cellulose acetate phthalate as described in Simmons U.S. Patent No. 2,327,828, issued Aug. 24, 1943. By the use of that material, it is possible to provide an antihalation layer of colloidal carbon finely dispersed in a coating solution diluted with organic solvents to obtain the desired coating consistency. Using a carrier of that type the antihalation layer is removable upon treatment in alkaline photographic developers. Cellulose acetate phthalate, although having many desirable properties for this purpose, has been prone to create problems of transfer of the antihalation material to a gelatin photographic emulsion when the emulsion and the backing contact each other at comparatively high relative humidities and temperatures. Defects are occasionally encountered in the use of cellulose acetate phthalate backing layers, particularly with certain photographic products of the color film type. These defects have been generally referred to as moisture mottle.

One object of our invention is to provide backing layers having greater hydrolytic stability than those in which cellulose acetate phthalate is employed. Another object of our invention is to provide antihalation layers which act to reduce the moisture mottle of certain photographic films and result in backing transfer thresholds at higher relative humidities than with cellulose acetate phthalate 3,392,022 Patented July 9, 1968 backing layers. Another object of our invention is to provide antihalation layers which are especially adapted for easy removability in alkaline photographic developers. Other objects of our invention will appear hereinafter.

We have now found that antihalation coatings for photographic film comprising cellulose acetate hexahydrophthalate or cellulose acetate tetrahydrophthalate and antihalation material results in improved photographic products compared with those having antihalation layers of the cellulose acetate phthalate type. The antihalation layers of our invention are easily applied to photographic film supports from organic solvents and flexible layers of good adherence to the film support results. These layers are easily removed by use of alkaline developers which convert cellulose acetate hexahydrophthalate or cellulose acetate tetrahydrophthalate to the form of a salt which is water-soluble. However, in the alkaline developer solu tions these salts dissolve slowly. Unexpectedly, we have further found, that by incorporating an alkali soluble lower alkylmethacrylate-methacrylic acid copolymer in the above described antihalation coating compositions, improved antihalation layers are obtained which are characterized by not only good halation protection but also by their greatly superior ease of removability right in the alkaline developers. For example, the antihalation coatings of the invention containing alkylmethacrylatemethacrylic acid copolymers in admixture with the cellulose acetate hexahydroor tetrahydrophthalate come off clean (as very fine particles) from the film support in the alkaline developer solutions, i.e. requiring no wiping or other physical removal treatment, whereas the antihalation coatings of the invention containing none of said copoiymers, while very useful, still require a bufiing or wiping step after treatment with the alkaline developer solutions for complete removal of all backing remnants. This procedure complicates photographic film processing and requires expensive equipment. The presence of the fine polymeric particles in the developer does not adversely affect developer activity. In this connection, it was also found that antihalation coatings comprising only the said copolymer and antihalation material, i.e. containing no cellulose acetate hexahydroor tetrahydrophthalate component, come oit in undesirably large flakes or sheets which tend to contaminate the alkaline processing solution and interfere with the operation. Accordingly, it will be apparent that while all the antihalation coatings of the invention are superior as compared to prior art coatin gs such as the aforementioned cellulose acetate phthalate coatings, it is the combination of the cellulose acetate hexahydroor tetra-hydrophthalate with the said copolymeric material, together with the antihalation material, which produces coatings especially adapted for easy and clean removal from film supports in alkaline developers. Such combination is a preferred embodiment of the invention.

Other embodiments of our invention include the use of the antihalation layers of the invention containing a major amount of, or only the hexa'hydroor tetra-hydrophthalate material on photographic films such as multilayer color films requiring high moisture resistance. However, for certain color films using carbon as the antihalation material it is desirable to include some of the copolymer material to facilitate removal of the antihalation layer. Films not requiring the utmost moisture resistance property in the antihalation layer advantageously contain both the phthalate and copolymer materials.

Cellulose acetate hexahydroor tetrahydrophthalates which are useful in the application of antihalation layers to photographic film support are described in US. patent application Ser. No. 282,230 of Carlton L. Crane, filed May 22, 1963, now abandoned and French Patent No.

1,393,927, Feb. 15, 1965, corresponding thereto. In this process, cellulose acetate having 35-42% acetyl content is dissolved in a lower fatty acid and hydrolyzed with mineral acid to acetyl content of about 26-34% followed by esterification with the appropriate polycarboxylic acid anhydride using basic catalyst. These cellulose esters are applied to the film base in solution in organic solvents and may be either in acid form or in the form of their salts. The cellulose acetate hexahydroand tetrahydrophthalates which have been found to be especially useful in the preparation of antihalation layers in accordance with our invention are those having a content of hexahydrophthalyl or tetrahydrophthalyl within the range of 18-38%, based on the total ester. Various combinations have been found to be useful as solvents for the mixture of cellulose ester and antihalation material which is to be applied to the film base and the solvents are selected by the operator in accordance with those which are most useful in connection with the particular film support to which the layer is ap plied. Antihalation layers in accordance with our invention may be applied to various types of film supports such as of cellulose nitrate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, or of synthetic resin as, for example, polycarbonate, polystyrene or polyester film base.

The antihalation material used may be a carbon dispersion, dispersed colloidal carbon being commonly known and used in the photographic art in the preparation of antihalation layers. However, an antihalation dye can be used instead of colloidal carbon. The dye may be directly mixed with the cellulose ester, ie with cellulose acetate hexahydroor tetrahydrophthalate, or the cellulose ester layer may be applied to the support and a dye coating may be applied thereover so as to penetrate into the surface only of the cellulose ester coating. Proceeding in this manner avoids migration of the dye into the film support itself particularly in the case of a dye which may have a tendency to migrate from one layer to another. The antihalation material employed in the cellulose ester layer is present in suflicient amount to absorb to a substantial degree the light which passes through the film base upon exposing the photographic film. The carbon used is desirably one which can be dispersed with the antihalation binder either by a hot milling technique, by a homogenizer, by a Kady mill or by some type of paint mill, e.g., Peerless carbon black sold by the Columbian Carbon Co.

In the preparation of the cellulose ester-copolymer antihalation coating compositions of the invention, the lower alkylmethacrylate-methacrylic acid copolymer is simply incorporated with the cellulose acetate hexahydroor tetrahydrophthalate, with or without antihalation material, by conventional methods for obtaining homogeneous mixtures such as agitation, mixing, mechanical blending, etc., preferably in a mutual solvent for these polymeric materials. The proportions of cellulose acetate hexahydroor tetrahydrophthalate to the said copolymer can vary over a wide range depending, for example, upon the degree of moisture resistance or removability required of the antihalation layer. From about 25 to 75% of the former and 75 to 25% of the latter, based on the total weight of these two components, is preferred. The total solids in the coating compositions can advantageously range from about 2 to or even more if desired. The thickness of the antihalation layer from the above compositions can vary from 0.00005 to 0.00010 inch, although excellent results are obtainable with layers of greater thickness. These compositions are applied to the support materials, and more especially to cellulose ester film supports, e.g. cellulose acetate, in the manner previously described herein. The antihalation dye compounds may also be either incorporated in the coating compositions or they may be applied from suitable solutions thereof over the coated layer. If desired, conventional antistatic materials may also be included in the above described compositions.

Suitable alkali dispersible lower alkylmethacrylatemethacrylic acid copolymers, wherein the said alkyl group 4 is straightor branch-chained, and contains from 1 to 4 carbon atoms, include methylmethacrylate-methacrylic acid, ethylmethacrylate-methacrylic acid, propylmethacrylate-methacrylic acid, isopropylmethacrylate-methacrylic acid, butylmethacrylate-methacrylic acid, etc. copolymers, wherein the molar ratios of the alkylmethacrylate component to the methacrylic acid component are advantageous for good alkali-dispersibility from 1:3 to 3:2 (equivalent on a weight basis to approximately from 28 to 72% of alkylmethacrylate units and conversely from 72 to 28% of methacrylic acid units). Such copolymers are known substances, and methods for their preparation are well known to the art. These copolymers while generally soluble in aqueous alkaline solutions, in the presence of the cellulose acetate tetrahydroand hexahydrophthalates dissolve slowly in the alkaline photographic solutions. It is not understood how these cellulose estersand copolymers coact so as to effect removability of the antihalation as fine particles in the alkaline developer solutions.

Our invention will now be described with particular reference to the accompanying drawing. As shown in the drawing, a support 10 of any suitable material such as cellulose ester or synthetic resin is coated with a photosensitive emulsion layer 11 or with a suitable subbing layer (not shown) between the support 10 and the emulsion layer 11 and on the opposite side with an antihalation layer 12 consisting of cellulose acetate hexahydroor tetrahydrophthalate, preferably in admixture with a copolymer of a lower alkylmethacrylate and methacrylic acid, and dispersed thereon colloidal carbon or carrying a dye having antihalation properties. Such antihalation coatings when applied to photographic film may give an optimum density to white light of from 0.1-2.0 in ordinary circumstances of use.

The following examples are illustrative of our invention.

Example 1 There was applied to a cellulose triacetate film support on one side a gelatin-silver halide photographic emulsion layer and on the opposite side an antihalation layer from a coating composition composed of the following:

Percent Cellulose acetate hexahydrophthalate containing approximately 25% hexahydrophthalyl 3.20 Colloidal carbon, dry weight 1.30 Actone 10.00 Methyl Cellosolve 30.00 Water 18.00 Ethyl alcohol 37.50

Percent Cellulose acetate hexahydrophthalate having a hexahydrophthalyl content of 27.5% 3.50 Acetone 70.00 Methyl alcohol 26.50

Over this layer a second coating was applied from a composition having the following formula:

Percent Yellow dye-1-ethyl-2-p-hydroxy-styrylquinoliniump-toluene sulfate 0.60 Magenta dye-sodium salt of diamino disulfomethylfuchsonium sulfonate 0.50 Sodium hydroxide, 3 N 0.30 Amonium hydroxide (28%) .05 Methyl Cellosolve 10.00 Methyl alcohol 88.55

By applying the coating in this fashion, the antihalation dye penetrates into the surface of the cellulose ester coating but there was no migration of the dye to the film base proper. There was thus obtained a photographic film having an antihalation backing which resisted mottling and the like under conditions of high temperature and high relative humidity. The antihalation coating was readily removed after the film had been processed in alkaline developing solution.

Example 3 This example illustrates an embodiment of the invention wherein a mixture of cellulose acetate hexahydrophthalate and a lower alkylmethacrylate-methacrylic acid copolymer was employed as the carrier for the antihalation compound.

There was applied to a cellulose triacetate film support on one side a gelatin-silver halide photographic emul sion layer, and on the Opposite side a layer having the percent by weight formulation:

Percent Methyl methacrylate-methacrylic acid copolymer (1:1 mole ratio of ester to acid components) 2.00 Cellulose acetate hexahydrophthalate (36% hexahydrophthalyl) 1.50 Acetone 11.00 Methyl Cellosolve 27.00 Ethyl alcohol 40.40 Distilled water 18.00 Syloid #311 (a trade name for a synthetic silica matting agent sold by Davison Chemical Corp.) 0.10

Over this layer a second coating was applied from a composition having the percent by weight formulation:

Percent Yellow dye-bis[l-(p-sulfophenyl) 3 methyl 5 pyrazo1one(4)methine oxonol a- 0.80 Yellow dye-4[ (3-ethyl-2 (3H -benzoxazolylidene 2-butenylidene]-3-methyl 1 p-sulfophenyl-Z- pyrazolin-S-one, monosulfonated 0.30 Magenta dye-4[(3-ethyl 2(3H) benzoxazolylidene)ethylidene1-3-methyl 1 p-sulfophenyl-Z- pyrazolin-S-one, monosulfonated 0. 0 Magenta dye-bis[1-(p-sulfophenyl)-3-methyl-5-pyrazolone-(4)]trimethine oxonal 0.20 Cyan dye bis[l-(p-sulphophenyl)-3-methyl-5-pyrazolone-(4)]-pentamethine oxonol 0.80 Triethanolamine 1.10 Distilled water 10.00 Methyl Cellosolve 7.50 Methyl alcohol 79.10

There was thus obtained a light-sensitive photographic film having an antihalation backing which resisted mottling and the like under conditions of high temperature and high relative humidity, and which was easily and cleanly removed in fine particulate form from the film support on processing in conventional alkaline developing solution.

It will be understood that the solvent composition in above Example 3 can be varied substantially and still produce excellent antihalation layers. Thus, in the cellulose ester-copolymer coating composition, the acetone can vary about from 8 to 12%, the methyl cellosolve about from 18 to 35%, the distilled water about from to 20%, and the ethyl alcohol can vary sufiiciently to make up a total of 100% of composition. Methanol can replace the ethyl alcohol. Also, the cellulose acetate hexahydrophthalate can be replaced wholly or in part by cellulose acetate tetrahydrophthalate. The mentioned silica is used as a matting agent and is optional, but when used it can vary advantageously about from 0.05 to 0.20%. Other silicas can also be used, if desired, such as Ludox AM (a trade name for an aluminum modified colloidal silica sold by E. I. du Pont de Nemours and Co.).

The dye compounds employed in the preceding example are well known. For example, the dye compounds used in above Example 3 are described in Gaspar US. Patent No. 2,274,782, issued Mar. 3, 1942, or in Heseltine US. Patent No. 3,148,187, issued Sept. 8, 1964. Other known antihalation dyes can also be used in our invention.

The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be elfected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. A photographic film support provided with a layer comprising a cellulose ester containing acetate radicals and radicals selected from the group consisting of hexahydrophthalyl and tetrahydrophthalyl and antihalation material.

2. Photographic film support in accordance with claim 1 wherein said layer also contains a copolymer of a lower alkylmethacrylate and methacrylic acid in the molar ratio of from 1:3 to 3:2 of said alkylmethacrylate to said methacrylic acid.

3. Photographic film support in accordance with claim 1 wherein said cellulose ester is cellulose acetate hexahydrophthalate.

4. Photographic film support in accordance with claim 1 wherein said cellulose ester is cellulose acetate tetrahydrophthalate.

5. Photographic film support in accordance with claim 3 wherein said antihalation material is colloidal carbon.

6. Photographic film support in accordance with claim 3 wherein said antihalation material is an antihalation dye compound.

7. Photographic film support in accordance with claim 2 wherein said cellulose ester is cellulose acetate hexahydrophthalate.

8. Photographic film support in accordance with claim 7 wherein said antihalation material is an antihalation dye compound.

9. A photographic film comprising a film support having on one side a gelatin-silver halide emulsion layer and having on the opposite side an antihalation layer comprising a cellulose ester containing acetate radicals and radicals selected from the group consisting of hexahydrophthalyl and tetrahydrophthalyl and antihalation material.

10. A photographic film in accordance with claim 9 wherein said antihalation layer also contains a copolymer of a lower alkylmethacrylate and methacrylic acid, in the molar ratio of from 1:3 to 3:2 of said alkylmethacrylate to said methacrylic acid.

11. A photographic film in accordance with claim 9 wherein said cellulose ester is cellulose acetate hexahydrophthalate.

12. A photographic film in accordance with claim 9 wherein said cellulose ester is cellulose acetate tetrahydrophthalate.

13. A photographic film in accordance with claim 11 wherein said antihalation material is colloidal carbon.

14. A photographic film in accordance with claim 11 wherein said antihalation material is an antihalation dye compound.

15. A photographic film in accordance with claim 10 wherein said cellulose ester is cellulose acetate hexahydrophthalate.

16. A photographic film in accordance with claim 15 wherein said antihalation material is an antihalation dye compound.

17. An antihalation composition comprising a cellulose ester containing acetate radicals and radicals selected from the group consisting of hexahydrophthalyl and tetrahydrophthalyl, and antihalation material.

18. An antihalation composition in accordance with claim 17 wherein said composition also contains a copolymer of a lower alkylmethacrylate and methacryiic acid, in the molar ratio of from 1:3 to 3:2 of said alkylmethacrylate to said methacrylic acid.

19. An antihalation composition in accordance with claim 18 wherein said cellulose ester is cellulose acetate hexahydrophthalate.

20. An antihalation composition of claim 19 wherein said antihalation material is an antihalation dye compound.

References Cited UNITED STATES PATENTS Malm 96-84 Staud 96-84 Simmons 9684 Thompson et a1. 96-84 NORMAN G. TORCHIN, Primary Examiner.

m R. H. SMITH, Assistant Examiner. 

